In the first stage of the project "Synthesis and characterization of polyelectrolytes based on polysaccharides with different chain flexibility (Pul, Chit, Dex, Cel) in soluble or hydrogel form and studies of aggregation/adsorption of inorganic and organic particles in aqueous and non-aqueous dispersion medium” were addressed several strategies for the synthesis of ionic, soluble and crosslinked polymers (hydrogels), based on polysaccharides, able of interacting with inorganic and organic particles, dispersed in model suspensions/emulsions. In order to achieve the objectives of this stage, the following activities were carried out: 1.1. Synthesis and characterization of the chemical composition of soluble PEs (polysaccharides with cationic grafts); 1.2. Preparation and physico-chemical characterization of hydrogels in the form of monolith and/or membranes based on Chit, Pul, DxS by cryogelification technique; 1.3. aggregation of inorganic particles (zirconium silicate, clays, etc.) in aqueous/non-aqueous dispersion medium; 1.4. Adsorption of one-component pesticides by hydrogels by the freezing technique, the results of which are presented as follows:

• Samples of soluble cationic polysaccharides based on pullulan with tertiary or quaternary ammonium amine groups with or without hydrophobic groups were synthesized and characterized (elemental analysis, ¹H- and ¹³C-NMR spectroscopy, IR). The synthesis conditions (molar ratio between reaction partners, temperature, duration) were adapted to each type of macromolecular compound so as to obtain polyelectrolytes with a well-defined structure;
• Samples containing tertiary amine groups or quaternary ammonium groups were selected for aggregation of inorganic particles (zirconium silicate (kreutzonite), clays, TiO₂, etc.) in aqueous (different pHs) and aqueous/non-aqueous (water/methanol (%): 90/10 and 50/50) dispersion medium;
• All investigated inorganic particles were successfully aggregated and removed (more than 95%) by Pg-pAPTAC2 and DMAPA_0.16-P polymers from dispersions prepared with water regardless of the pH or water / methanol composition (%, v / v): 90/10 and 50/50; optimal polymer doses ranged from 0.4 mg L^-1 to 1.4 mg L^-1.

     Novel porous hydrogels were prepared by cryogelation technique and characterized (FT-IR, NMR, and SEM):

• Porous hydrogels based on Chit and oxidized CMC (CMCox), as membranes were prepared using different molar ratios between -NH₂ groups of Chit and -CHO groups of CMCox.
• Physically cross-linked hydrogels based on Chit and DxS were designed by varying the molar ratio between -NH₂ groups of Chit and -SO₃Na groups of DxS, the molar mass of DxS, and the gel preparation temperature.
• Chit-based porous hydrogels, as monoliths were obtained by combining cryogelation with porogen leaching methodology. These hydrogels have been successfully used to remove Fastac 10 EC insecticide from aqueous solutions.
• Macroporous interpenetrating hydrogel networks based on PHEMA and Pul were also successfully synthesized.

     Samples of cationic polymers based on polysaccharides, soluble or in gel form, synthesized and tested in the aggregation and sorption experiments in the first stage of the project proved to be highly effective in reducing (90-95%) the inorganic contaminants (kreutzonite, TiO₂, kaolin) and organic (complex formulation of pyrethroid insecticide-Fastac 10 EC) investigated, thus expanding the range of biodegradable, non-toxic and cheap ionic materials with potential applications in the field of wastewater purification from the ceramic and pesticides industries as well as in agriculture.

All the objectives proposed for 2021 have been fully met, the results obtained being disseminated as follows: 

Published articles 

1.Efficacy of quaternary ammonium groups based polyelectrolytes for the reduction of various pesticide formulations content from synthetic wastewater, L. Ghimici, M. Nichifor, Sep. Purif. Technol. 276 (2021) 119325. https://doi.org/10.1016/j.seppur.2021.119325 (Q1, FI= 7.312)

2. Synthesis of Thiourea-Graft-Polyethyleneimine and Its Performance in Flocculation of Some Inorganic Particles,  C.-A. Ghiorghita, L. Ghimici, G.-L. Ailiesei,  Ind. Eng. Chem. Res. 60 (14) (2021) 5167–5175. https://doi.org/10.1021/acs.iecr.1c00555, (Q2,FI= 3, 72)

3. Physically cross-linked chitosan/dextrin cryogels entrapping Thymus vulgaris essential oil with enhanced mechanical, antioxidant and antifungal properties, M. V. Dinu, A.C. Grădinaru, M. M. Lazăr, I. A. Dinu, I. E. Răschip, N. Ciocarlan -. International Journal of Biological Macromolecules 184 (2021) 898–908. https://doi.org/10.1016/j.ijbiomac.2021.06.068 (Q1, FI = 6.953)

4. Analysis of copper(II), cobalt(II) and iron(III) sorption in binary and ternary systems by chitosan-based composite sponges obtained by ice-segregation approach, Maria Valentina Dinu, Doina Humelnicu, Maria Marinela Lazăr, Gels 7 (2021) 103. https://doi.org/10.3390/gels7030103 (Q1, FI = 4.702)

Communications

1. Aqueous Solutions of chitosan: viscometric and flocculation properties, Cristina Eliza Brunchi, L. Ghimici, Proceceeding of the 10th International Conference TEXTEH  Bucharest, Romania 2021, p. 123-129. DOI: 10.35530/TT.2021.21

2.Cryogenically-structured composite biomaterials, M.V. Dinu, M.M. Lazăr, I.E.Răschip, Congresul Internațional „Pregătim viitorul promovând excelența”, Universitatea „Apollonia” din Iași, 1-3 march 2021.

3. Chitosan aqueous solutions: viscometric and flocculation properties, C.-E.  Brunchi, L.Ghimici,  The 10th International Conference TEXTEH 2021, Bucharest, Romania October 21-22, 2021.         2. 4. 4. Formation of 1D-oriented structure in chitosan-based hydrogels, M.M. Lazăr, M.V.Dinu, Congresul Internațional „Pregătim viitorul promovând excelența”, Universitatea „Apollonia” din Iași, 1-3 march 2021.

5. 3D anisotropic polysaccharide-based cryogels as multifunctional eco-friendly materials for wastewater treatment, M.V. Dinu, M.M. Lazar, I.A. Dinu, I.E. Raschip, C.-A. Ghiorghita, L. Ghimici, 11th International Conference on Environmental Engineering and Management (ICEEM11), Muttenz, Switzerland, 8–10 September 2021.

6. Synthesis and flocculation performance of thiourea-g-polyethyleneimine, C.-A. Ghiorghita,  L. Ghimici, Congresul Internațional „Pregătim viitorul promovând excelența” , Universitatea „Apollonia” Iași, 1-3 march 2021-Poster.

         In the second stage of the project "Study of the interdependencies between PEs characteristics, dynamic properties and the ability of aggregation and adsorption of pesticide mixtures" both the physico-chemical properties of some polysaccharide-based ionic polymers (pullulan, dextran, chitosan), soluble and cross-linked (microspheres/cryogels) and the ability to remove pesticide mixtures from model dispersions have been investigated. To achieve the objectives of this stage, the following activities were carried out: 2.1. Viscosity studies of soluble cationic polymers PEs in aqueous solution both in the absence and presence of salt; 2.2. Preparation and physical-chemical characterization of microspheres based on Pul, Dex; 2.3. Aggregation and adsorption of pesticide mixtures in the presence of soluble cationic PEs in combination with a neutral polymer or not, and of hydrogels (microspheres and cryogels) whose results are presented, as follows:

• The viscosimetric behavior of solutions of cationic derivatives of pullulan (Pul), with pendant quaternary ammonium salt groups in aqueous solution, both in the absence and presence of low molecular salt, was investigated. The following hydrodynamic parameters were quantified from the viscometric measurements: the intrinsic viscosity ([η]), the hydrodynamic interaction parameter (B) and the characteristic specific hydrodynamic volume ([η]*), which provide information on both the conformation and the hydrodynamic volume of the polymer chains as well as about the competition between polymer-polymer and polymer-solvent interactions.
• The following types of microsferes have been synthesized and characterized (FT-IR, SEM, TG-DTG) următoarele tipuri de microsfere: 

• • Microspheres based on pullulan (Pul) by cross-linking in suspension of Pul with epichlorohydrin (EPCH). They were functionalized with cationic groups (tertiary amine) with a content of 1.2 mechiv./g.
  • Microspheres based on dextran (Dex) by reticulation in suspension of Dex with EPCH and  subsequently functionalized with 2.45 mechiv/g tertiary and quaternary ammonium amine groups.

• Samples of Pul-based cationic PEs of type P-g-pAPTAC and DMAPAx-P were  selected for the aggregation of pesticide particles (complex commercial formulations) (Confidor Oil (CO), Confidor Energy (CE), Decis (Dc), Karate Zeon (KZ), Fastac 10EC (F)) in order to remove them from mono -/ two components model emulsions.
• All investigated insecticide particles were successfully removed (removal efficiency between 84-90%) in the presence of P-g-pAPTAC and DMAPA0.7-P samples, the optimal polymer doses varying in the range of 0.6 mg L-1 – 2.2 mg L-1.
• Crogels based on chitosan (Chit) and carboxymethyl cellulose (CMC) or oxidized carboxymethyl cellulose (CMCox) have been used to remove multicomponent fungicide formulations, namely Dithan (Dt), Melody Compact (MC), Curzate Manox ( CM) and Cabrio Top (CT). These sorbents removed the MC fungicide most effectively. The maximum theoretical adsorption capacities of Chit/CMC and Chit/CMCox3 sorbents for this fungicide were 62.74 mg/g and 146.68 mg/g, respectively.
• Microspheres based on Pul (Pul/DMA) and Dex (Dex/DEA) have been shown to be good sorbents for Melody Compact (MC) particles. The removal process of the fungicide formulation is an effective and complex one, with removal efficiencies between 89.5-95% being recorded by adsorption on the surface of the microspheres followed by flocculation of the MC molecules. The optimal doses of microspheres were 5 mg Pul/DMA and 2.5 mg Dex/DEA, the differences being due to the lower content of cationic groups in Pul microspheres.

Soluble cationic derivatives of Pul and polymer samples in the form of cryogels/microspheres, synthesized in steps 1 (soluble polymers and cryogels) and 2 (microspheres based on Pul and Dex) proved to be effective flocculants and adsorbents for the mixtures of investigated pesticides (removal efficiency 84-95%), a fact that recommends them for potential uses in the field of wastewater containing such highly toxic contaminants. 

All the objectives proposed for the year 2022 were fully met, the results obtained being disseminated as follows:

Published articles 

1. Grafted Pullulan Derivatives for Reducing the Content of some Pesticides from simulated Wastewater, Luminita Ghimici, Marieta Constantin and Maria-Magdalena Năfureanu, Polymers 14 (2022) 2663-2667. https://doi.org/10.3390/polym14132663. (Q1, FI= 4.967)

2. Macroporous 3D Chitosan Cryogels for Fastac 10EC Pesticide Adsorption and Antibacterial Applications, Ionel Adrian Dinu, Luminita Ghimici and Irina Elena Raschip, Polymers 14 (2022) 3145 -3160. https://doi.org/10.3390/polym14153145. (Q1, FI= 4.967)

3. Aminopolycarboxylic acids-functionalized chitosan-based composite cryogels as valuable heavy metal ions sorbents: Fixed-bed column studies and theoretical analysis,  Maria Valentina Dinu, Ionel Humelnicu, Claudiu Augustin Ghiorghita, Doina Humelnicu, Gels 8 (2022) 221. https://doi.org/10.3390/gels8040221 (Q1, FI = 4.432)

Communications

1. Removal of some commercial pesticides formulations by polyelectrolytes based flocculants, L.Ghimici, M. Constantin, M. M. Năfureanu,  12th International Conference on Materials Science and Engineering, Bramat 2022, Brasov, 9-12 martie 2022.

2. Chitosan Efficacy as Flocculant in Removal of Some Pesticides, C. E. Brunchi, M. M. Năfureanu, L. Ghimici, 12th International Conference on Materials Science and Engineering, Bramat 2022, Brasov, 9-12 martie 2022.

3. Facile Synthesis of Thiourea-Polyethileneimine and its Application as Flocculant to Separate Inorganic Particles in Model Suspensions,  C.A. Ghiorghiță, G. L. Ailiesei, L. Ghimici, 12th International Conference on Materials Science and Engineering, Bramat 2022, Brasov, 9-12 martie 2022.

4. Macroporous Three-Dimensional Chitosan Cryogels for Pesticide Adsorption and Antibacterial Applications,  M.V. Dinu, L. Ghimici, I. E. Răschip, 12th International Conference on Materials  Science and Engineering, Bramat 2022, Brasov, 9-12 martie 2022.

5. Recent Advances in multicomponent polymer systems with controlled 3D architectures, M.V. Dinu, M.M. Lazar, I.E. Raschip , C.A. Ghiorghita, I.V. Platon, Congresul International „Pregatim viitorul promovand excelenta”, Universitatea „Apollonia” Iași, 28 februarie - 2 martie 2022

6. Development of multifunctional bioactive polysaccharide-based composite hydrogel by a dual ice-templating strategy, M.V. Dinu, I.E. Raschip, C.A. Ghiorghita, M.M. Lazar, I.V. Platon, Conferinta „EPF 2022- European Polymer Congress” , Praga, 22 iunie-1 iulie 2022.